The present discovery relates to a hydraulic shield support such as may be used in underground mining. The shield support includes at least two adjustable-length hydraulic props borne on base shoes and supporting a shield, which may be connected through a control bank to a hydraulic fluid supply system. A pressure in excess of the pressure of the hydraulic fluid may be applied in the set condition of the shield support. The shield support may be a stope shield support, but the present discovery is not limited thereto.
In deep mining, hydraulic supports are used to keep the face or working area free and to support the so-called roof. In particular, they may take the form of lemniscate shields, as for example, disclosed in U.S. Pat. Nos. 4,815,898, 6,056,481 or 5,743,679, all of which are hereby incorporated by reference. The main or roof shield is supported by double acting, preferably multiple-stage hydraulic props, which are counter-borne on the base shoes. Setting or removing the shields takes place as a function of pilot signals from an electrical control unit, which automatically activates the actuators, such as e.g. electromagnets, allocated to the hydraulic actuation valves in the control banks. In the hydraulic shield supports currently used in deep mining, a setting pressure of approximately 320 bar may be applied to the hydraulic props and may subsequently be increased to a maximum pressure of approximately 400 bar to support the load of the rock. Both pressures are applied through the control bank.
Provision of the increased pressure through a second, supplementary supply system is known from DE 101 16 916 A1, hereby incorporated by reference. The provision of a principal supply system for a pressure of approximately 300 bar may keep the volume flows, which the supplementary supply system must be able to deliver for the pressure of approximately 400 bar, low, and mean that the supplementary supply system can be embodied with comparatively small cross-sections. This approach requires the laying of a second hydraulic supply system throughout the entire face, in addition to the principal supply system.
There is a constant demand for longer faces and higher-capacity winning and conveyor systems for the economic mining of coal or other minerals from deep faces. Consequently, the roof surface area to be supported by shield supports in the face area increases constantly. To support the rock, it is thus necessary to increase the resistance which can be applied to the shield by the hydraulic props. Fundamentally, the number of hydraulic props, their effective diameter or the pressure of the hydraulic fluid may be increased for this purpose.